Researchers at the Marcus Institute of Integrative Health at Thomas Jefferson University studied the brain responses of pilgrims on an Ignatian retreat and published their results in Religion, Brain and Behaviour.

Dr Andrew Newberg, director of research at the institute, said: “Since serotonin and dopamine are part of the reward and emotional systems of the brain, it helps us understand why these practices result in powerful, positive emotional experiences.

“Our study showed significant changes in dopamine and serotonin transporters after the seven-day retreat, which could help prime participants for the spiritual experiences that they reported.”

Dopamine is known as the “pleasure chemical” but is involved in a wide range of brain functions, from the control of attention to movement. Serotonin is often called the “feel-good hormone” and is involved in emotional regulation and mood.

Post-retreat scans revealed decreases in dopamine transporter and serotonin transporter binding, which could make more of the neurotransmitters available to the brain.

The study was conducted by the Fetzer Institute and included 14 Christian participants aged 24 to 76 who attended an Ignatian retreat and practised the spiritual exercises of Jesuit founder St Ignatius Loyola.

After morning Mass, the people on retreat spent the majority of the day in silence, with prayer and reflection, and met daily with a spiritual director.

Participants revealed a significant positive change in health, tension and tiredness and reported feelings of self-transcendence which researchers belief correlates with the rise in dopamine levels.

Dr Newberg said: “In some ways, our study raises more questions than it answers. Our team is curious about which aspects of the retreat caused the changes in the neurotransmitter systems and if different retreats would produce different results. Hopefully, future studies can answer these questions.”